1. Field of the Invention
This invention relates to a fluidic gauge, and, more particularly, to a frequency modulated fluidic gauge having no moving parts for monitoring a characteristic of a continuously moving strand-like material.
2. Description of the Prior Art
Prior art fluidic gauges for monitoring a characteristic of a continuously moving strand-like material generate a pneumatic output pressure signal which is proportional to a characteristic of the material. However, as the diameter of the material is decreased, the dimension of an enclosed channel of a suitable sensor head, which can be used to monitor the desired characteristic, also must be decreased accordingly, thereby resulting in a significant increase in the fluidic resistance of the channel. The time constant of the gauge includes the fluidic resistance of the channel multiplied by the line capacitance between the channel and a pressure responsive transducer. Thus, for material diameter and/or denier measurements of approximately 0.006 inch to approximately 0.008 inch within about a 0.010 inch diameter channel, the time constant of the readout circuit could conceivably rise to approximately one or two seconds. Under these circumstances, if the strand-like material were moving through the gauging channel at a speed of 3,000 feet per minute, and if the circuit response time is approximately two seconds, one hundred feet of bad material could pass through the gauge before a suitable response could be made to a machine. This, of course, can lead to an accumulation of a large and expensive amount of waste, which could render the pneumatic sensing gauge inappropriate for use.
Thus, as seen above, fluidic gauges which provide a pressure sensitive readout for monitoring a characteristic of strand-like material are generally unsuitable for monitoring strand-like material having a diameter less then approximately 0.008 inch. Furthermore, if the gauge is located a significant distance away from a pressure transducer, the line capacitance will be quite large, and the circuit time constant may be too large for useful operation even when more moderately dimensioned strand-like material is being measured.